Elements at Risk. Demographic changes will directly affect the elements at risk by means of increases or decreases in the population and/or the population density. Such changes may be effected by the construction of new buildings (a more likely scenario) or by more (or fewer) people inhabiting existing buildings. Each is likely to have an effect on both the local population and the local population density and, dependent upon the spatial interaction with the landslide hazards, may increase the elements at risk in terms of both buildings and people. Indeed, the construction of new buildings is likely to place people in previously unoccupied areas and may thus introduce new risks. Demographic changes also affect the elements at risk on linear transport infrastructure. An increase in the population of a town or village inevitably increase the traffic levels on roads connecting it to the outside world and thus the number, and value, of vehicles and road users using it at any given point in time also increases (see also Section 3.3.2).
Elements at Risk. New infrastructure construction will introduce additional elements at risk, which are likely to be of higher value than the elements that they replace. Such infrastructure also can provide a degree of protection to elements previously at risk: linear infrastructure cuttings can function, albeit inadvertently, as a debris trap for example providing protection to elements at risk further down slope It is also worth noting that as infrastructure ages its condition may also deteriorate, regardless of the maintenance regime applied during its in-service life. While this implies that its value may decrease, in monetary terms as the costs of restoration to an as new’ condition increases, its value as an asset is likely to be dependent upon, and proportionate to, the population that it serves and, by extrapolation, depends upon it for transport, electricity, etc (see also Section 3.2.1).
Elements at Risk. The statistics institute INSEE provides extensive information about the residential buildings of the towns in the area studied: for example the number of residences (but also their status as either main residences, second homes or vacant dwellings) for each census between 1968 and 2006. However, only values for 1990, 1999 and 2006 were used to extrapolate future values, in order to reflect the current trends. In order to forecast future values for 2030, and thanks to a quite steady evolution trend, a linear regression has been performed (Table 18). Based on the forecasts of main residences and of population, the average number of dwellers has been computed. This indicator is a useful one to assess the population potentially exposed to the effects of landslide hazards. Table 18 Evolution of the number of residences and related indicators from 1990 to 2006 and predictions for 2030 Barcelonnette 1990 1999 2006 2030 Residences 2 809 2 965 3152 3648 Main residences 1 277 1 261 1368 1471 Second homes 1 141 1 451 1513 2121 Vacant dwellings 391 253 271 56 Average number of dweller (main r.) 2.3 2.2 2.1 2.4 Enchastrayes 1990 1999 2006 2030 Residences 1 852 1 911 2046 2312 Main residences 190 216 200 225 Second homes 1 659 1 686 1830 2052 Average number of dweller (main r.) 2.5 2.3 2.2 2.4 Faucon-de-Barcelonnette 1990 1999 2006 2030 Residences 174 184 221 283 Main residences 76 85 116 169 Second homes 81 92 102 133 Average number of dweller (main r.) 2.6 2.4 2.6 2.2 Jausiers 1990 1999 2006 2030 Residences 941 984 1084 1280 Main residences 316 335 398 508 Second homes 554 605 648 788 Vacant dwellings 71 44 38 0 Average number of dweller (main r.) 2.5 2.5 2.5 2.5 Saint-Pons 1990 1999 2006 2030 Residences 365 444 495 693 Main residences 193 249 280 414 Second homes 133 165 200 298 Vacant dwellings 39 30 14 0 Average number of dweller (main r.) 2.6 2.6 2.4 2.0 A pertinent fact is the number of second homes in the studied site. Table 19 shows that the ratio of second house exceeds 40% in all the towns, and is near 90% for Enchastrayes. It also indicates that these ratios are not expected to change a lot in the next 20 years. Table 19 Predicted evolution of the proportion of secondary homes in the towns of the studied site 2006 2030 Barcelonnette 48% 58% Enchastrayes 89% 89% Faucon-de-B. 46% 47% Jausiers 60% 62% Saint-Pons 40% 43% The average number of dwellers for the main residences of the towns is also expected to remain relatively constant: this indicator will stay be...
